This invention relates to a structure for supporting a power unit for a vehicle in which a transmission is connected with a transversely disposed engine proper in a direction transversely of the body of a vehicle.
In general, front-engine and front-drive type vehicles are designed such that an engine proper is disposed transversely of the body of a vehicle so as to reduce the fore-and-aft dimension of an engine room thereby to englarge the space inside a passenger room. In such front-engine and front-drive type vehicles, a transmission housing enclosing a transmission gear train is connected with the engine proper through a clutch housing having a clutch received therein, and a differential gear housing with a differential gear therein is formed integrally with the transmission housing. Thus, the engine proper, the clutch, the transmission and the differential gear jointly constitute a power unit. There are a number of power units of this type in which a transmission housing is disposed on one side of a engine proper transversely of the body of a vehicle.
In this connection, there has been known a structure for supporting such a power unit on the vehicle body, as shown in FIG. 1 or FIG. 2, wherein reference numeral 1 designates a power unit; 2 an engine; 3 a clutch housing; 4 a transmission housing; and 5 a differential gear housing and an arrow X shows a forward direction of the vehicle. The power unit 1 is disposed in an engine room of a vehicle.
It is well known that the power unit 1 is caused under the engine operation to vibrate in a rolling manner around a predetermined straight line L passing through the center of gravity G thereof, the line L being called a principal axis of inertia. In general, the principal axis of inertia L extends diagonally or obliquely from the front end of the power unit 1 at the side of the engine proper 2 toward the rear end of the power unit 1 at the side of the transmission housing 4.
The structure for supporting the power unit 1, as illustrated in FIG. 1, is of a three-point support type having three support means 6a, 6b and 6c each comprising a rubber A, a bracket B attached to the power unit 1, and a bracket C attached to the vehicle body. One 6a of the support means is disposed on the principal axis of inertia L at the front end of the power unit 1 at the side of the engine proper 2 so as to support the engine proper 2 on a longitudinally extending side member 7a of the vehicle body; another support means 6b is disposed at the front end of the power unit 1 at the side of the transmission housing 4 in opposed relation to the support means 6a so as support the transmission housing 4 on another longitudinally extending side member 7b of the vehicle body; and the remaining support means 6c is disposed at the right side of the rear portion of the differential gear housing 5 so as to support the gear housing 5 on a dash board panel 8.
Incidentally, in FIG. 1, a restricting means 9 such as a buffer rod serves to restrict the rolling displacements of the power unit 1, but does not have any function of supporting the static load of the power unit 1.
With such a conventional power unit supporting structure of the three-point support type as described above, however, the support means 6b at the side of the transmission housing 4 and the support means 6c at the side of the differential gear housing 5 are away from the principal axis of inertia L so that they are caused to displace greatly during rolling displacements of the power unit 1. Accordingly, to reduce the rigidity against rolling of the support means 6b, 6c, it is necessary to decrease the spring constant or modulus of elasticity of the rubber A of each of these support means, but such a measure results in a remarkably reduced durability of the rubber A. In addition, since the support means 6c supporting the power unit 1 at side of the differential gear housing 5 is attached to the dash board panel 8 having a relatively low rigidity, as described before, there arises a problem in that vibrations of the power unit 1 is transmitted from the dash board panel 8 through the support means 6c to the interior of the passenger room, thus generating confined noises therein.
The above-described various problems are cleared by employing a two-point support type structure for supporting the power unit, as disclosed in the Japanese utility model application laid open to public inspection under Ser. No. 56-124526. Specifically, as shown in FIG. 2, there are provided two support means 10a, 10b, of which one 10a is disposed on or near the principal axis of inertia L at the front end of the power unit 1 at the side of the engine proper 2, whereas the other support means 10b is disposed on or near the principal axis of inertia L at the rear end of the power unit 1 at the side of the transmission housing 4. As a result, the respective support means 10a, 10b are disposed close to the principal axis of inertia L so that the amount of displacement of the power unit 1 acting on the support means 10a, 10b is reduced to substantial extent. Therefore, it is possible to improve the durability of the rubbers A of the support means 10a, 10b by increasing the spring constant or the modulus of elasticity thereof. Further, the support means 10a, 10b are attached to the opposed side members 7a, 7b, respectively, of the vehicle body so that noises confined in the passenger room can be reduced to a practical extent.
The above power unit support structure as illustrated in FIG. 2, however, involves another disadvantage in that accurate positioning of the power unit 1 is difficult and hence the position of the power unit 1 as installed would be displaced from its intended position, thus making it impossible to arrange the power unit 1 in proper and exact alignment with its associated parts or elements, because of two-point support structure. Moreover, such an improper positioning of the power unit 1 as displaced from its intended position causes a control rod (not shown) operatively connecting the gear train inside the transmission housing 4 with a shift lever (not shown) to be pulled to develop a so-called falling-off of the gears in the transmission housing 4.